Development of F1 hybrids in okra [Abelmoschus esculentus L. Moench]

Abstract

The project entitled “Development of F1 hybrids in okra [Abelmoschus esculentus L .Moench]” was carried out at the Instructional farm, College of Agriculture, Padannakkad during April-July 2019 to study heterosis and combining ability. The experiment was carried out in two parts. In part I, six diverse parents viz. AE5, AE16, AE18, AE20, AE30 and Salkeerthi were raised in a crossing block. They were crossed in half diallel fashion and 15 F1 hybrids were produced. In part II, the hybrids were evaluated along with their parents and checks in a randomized block design with 26 genotypes and three replications. Arka Anamika and Salkeerthi were used as OPV checks and Manjima and Arka Nikita as F1 hybrid checks. Parents of Manjima viz. Gowreesapattam local and IC282257 were also included as checks. Half diallel analysis was adopted for combining ability analysis. Relative heterosis, heterobeltiosis and standard heterosis using F1 hybrid Arka Nikita as standard check were worked out for all the characters. The estimation of heterosis revealed significant standard heterosis in the hybrids in desirable direction for growth, earliness and fruit traits. Three hybrids AE30 x AE18, AE30 x Salkeerthi and AE20 x AE30 showed highly significant positive standard heterosis for plant height. Three hybrids AE30 x Salkeerthi, AE30 x AE5 and AE18 x Salkeerthi showed highly significant positive standard heterosis for primary branches per plant. Two hybrids AE16 x AE5 and AE18 x AE5 showed highly significant negative standard heterosis for internode length. Two hybridsAE16 x Salkeerthi and AE20 x Salkeerthi showed highly significant negative standard heterosis for days to flowering. One hybrid AE18 x AE5 showed highly significant negative standard heterosis for days to 50% flowering. Five hybrids AE16 x AE30, AE16 x AE18, AE16 x AE5, AE20 x AE18, and AE30 x AE18 showed highly significant negative standard heterosis for node of fruit set. None of the hybrids showed significant positive standard heterosis for number of fruiting nodes. For fruit length AE20 x AE18 and AE20 x Salkeerthi showed significant positive standard heterosis. Three hybrids AE16 x AE30 AE5 x Salkeerthi and AE30 x AE5 showed significant positive standard heterosis for fruit girth. For fruit weight the hybrids AE30 xAE5, AE18 x AE5, AE20 x Salkeerthi, and AE20 x AE18 showed significant positive standard heterosis. None of the crosses showed significant positive standard heterosis for number of fruits per plant, marketable fruits per plant, marketable fruits per plant and yield per plant. The hybrid AE30 x Salkeerthi showed significant positive standard heterosis for mucilage content. Analysis of variance for combining ability revealed significant difference among the genotypes for all traits except fiber content, indicating sufficient variability for selection. The gca variance/ sca variance ratio indicated preponderance of non-additive gene action for all traits. None of the cross combinations exhibited high significant combining ability effects in desirable direction for all characters studied. The association of sca effects of outstanding crosses with gca effects of parents for each of the characters revealed that the high specific combiners involved high x high, high x low and low x low general combiners as parents. A combination of mean performance and gca effect was used to identify best parents and it revealed AE16, AE30 and AE20 as better performing parents for maximum number of characters. Even though the mean performance of AE16 was higher for fruit weight, number of fruiting nodes, yield per plant and marketable yield per plant, it was a poor general combiner for characters viz. number of fruiting nodes, fruit weight, and yield per plant compared to AE20 and marketable yield per plant compared to AE30. High gca effects for fruit yield in AE20 and AE30 were associated with good gca effects for number of fruits per plant and fruit weight. The parental lines AE20 and AE30 performed well even they were affected by yellow vein mosaic disease and fruit and shoot borer. Hence they can be used in further breeding program for higher yield. The parental line AE20 was the high general combiner for all of the three earliness attributes such as days to first flowering, days to 50% flowering, and node of fruit set, indicating its potential for exploiting earliness in okra. Promising crosses were identified based on mean performance, sca effect and standard heterosis for important growth and yield characters. None of the hybrids exhibited significant standard heterosis in the desirable direction for yield. Hence the hybrids showing lower value of negative standard heterosis were selected. The four better performing crosses identified were AE30 x AE5, AE20 x AE5, AE20 x Salkeerthi and AE30 x Salkeerthi. All these four crosses were good performers for marketable yield even when they were affected by yellow vein mosaic disease and shoot and fruit borer. In addition, these crosses showed good performance for few other yield contributing characters also. The cross AE30 x AE5 performed well for fruit weight, number of fruiting nodes and yield per plant. The cross AE20 x AE5 showed good performance for number of fruits per plant, marketable fruits per plant and yield per plant. AE20 x Salkeerthi was a good performer for fruit weight and fruit length. AE30 x Salkeerthi was good performer for plant height, primary branches per plant, internode length and mucilage content.